Pre-crash safety (PCS) systems that reduce or prevent collision damage between an obstacle (target) and an own vehicle have been produced. The obstacle is another vehicle, a pedestrian, a road structure, or the like present ahead of the own vehicle that has been detected by a target detection apparatus, such as an imaging apparatus or a radar apparatus. In PCS, a collision prediction time (time to collision [TTC]) is determined based on a relative distance between the own vehicle and the obstacle, and a relative speed or a relative acceleration. The collision prediction time is an amount of time until a collision occurs between the own vehicle and the obstacle. Based on the collision prediction time, a driver of the own vehicle is notified of approach by a warning apparatus of the own vehicle, or a braking apparatus of the own vehicle is operated.
However, when axial misalignment in which an attachment angle of the target detection apparatus becomes tilted occurs, an obstacle that is not actually positioned ahead of the own vehicle may be erroneously detected as being ahead of the own vehicle. Safety apparatuses, such as the warning apparatus and the braking apparatus, may be unnecessarily operated. The axial misalignment of the target detection apparatus may occur as a result of vibrations applied during vehicle traveling, an occurrence of light impact on the own vehicle, and the like.
Therefore, since the past, axial misalignment detection for the target detection apparatus has been performed. For example, when a radar apparatus is used as the target detection apparatus, misalignment information of the attachment angle of the radar apparatus is acquired from a movement trajectory of a road-side object detected by the radar apparatus. Then, as a result of a history of the misalignment information being statistically processed, an axial misalignment angle is calculated. The axial misalignment angle is the misalignment angle of the attachment angle of the radar apparatus. However, when the axial misalignment angle is calculated by statistical processing, time is required until determination accuracy regarding the axial misalignment improves.
Therefore, in PTL 1, in light of the fact that the axial misalignment of the radar apparatus serving as the target detection apparatus occurs as a result of light impact on the own vehicle, a determination that axial misalignment may have occurred is made when an acceleration sensor detects deceleration of a predetermined value or more. Then, the axial misalignment angle is calculated through use of a map that indicates a relationship between the deceleration detected by the acceleration sensor and the axial misalignment angle. As a result, axial misalignment caused by light impact can be quickly detected in a traveling state of the own vehicle.